Aluminum Weldability -CR 250 Trans cover

[MIKEDOGG]

I believe that the trans cover on my Honda CR 250 is made of a cast aluminum (correct me if i am wrong) and I am wondering if i can tig a small crack that has developed.

[FusionKing]

You Betcha!
Normally it must be apart and clean to do it.
At the very least it must be empty and vented. It can be horribly dificult to get to seal because of all the junk in the metal. Also the heat being drawn into the assembly and expansion/contraction can make it 10 times more difficult.
I make everyone disassemble and bring to me.
I only want to repair what I KNOW I can do and stand behind. I don't charge for failure.
Once you get it apart you can make it super clean and bevel out the crack and weld it up nice.
Good luck

[Suvi]

When welding aluminum with TIG, don't let tungsten stick out of the cup too much. Try no more than the diameter of the tungsen. And use atleast 1sec of post flow for every 10amps. So you will not contaminate the tunsten. I use these procedures and works for me every time. And ofcourse keep workpiece and weldingrods clean. Right before welding wipe the rod clean with acetone and clean the piece with stainless steel wirebrush.

[MIKEDOGG]

Right on, good news. I appreciate your responses because today I am taking the bike apart. Excellent advice on thoroughly cleaning the cover after disassembly and before prepping bevel. Also thank you for the words of wisdom with regards to electrode stickout, post flow minimum and cleaning of filler metal with acetone. I will post pictures of the crack and the weld. Thanks.

[Portable Welder]

Mike Dogg, You might want to search welding dirty aluminum.

The dirt on the welding rod is nothing in comparison to the dirty oil soaked aluminum.

I never clean my alum. welding rod, I never let it get dirty.

Magnesium is the only rod I clean because it oxidizes in my sealed rod holders.

I dont recommend vee grooving thin covers beforehand, it will naturaly vee groove as your cleaning the black sut out of the crack when trying to pull the contamination out of the aluminum.

[MR.57]

Most of the Honda motorcycle "aluminum" castings I have worked with seem to have an unusually high magnesium content. Whatever exact alloy Honda's using, it doesn't weld like the A356 that most automotive stuff is cast from. Oil contamination just adds one more problem variable. Call me a chicken, but I'd stop-drill the crack, epoxy over the thing and call it done. It isn't structural so a 100% strength repair isn't necessary.

[FusionKing]

Most of the Honda motorcycle "aluminum" castings I have worked with seem to have an unusually high magnesium content. Whatever exact alloy Honda's using, it doesn't weld like the A356 that most automotive stuff is cast from. Oil contamination just adds one more problem variable. Call me a chicken, but I'd stop-drill the crack, epoxy over the thing and call it done. It isn't structural so a 100% strength repair isn't necessary.

OMG!!!!! Is there a JB Welding forum out there???? Any crap that hinders welding stops good epoxy adhesion as well.
If you only knew how much of that CRAP I have removed by folks with good intentions only to find they have simply making the job they should have done in the first place much more dificult.

[Portable Welder]

Mr. 57,

Did you send your parts out to a metalurgist to find out that they have a high magnesium content.

You may also want to research ( Welding dirty aluminum )

Fushion king is right, I also get alot of people trying to save money with JB Weld and by the time it gets to me the repair cost is double because 1/2 my time is spent cleaning the JB weld out of the crevice.

[jardine]

I'm with MR.57. JB weld it. I've HAD to do it to quite a few of them over the years. I've tried to weld a few of them with poor results due to contamination and warpage. Once they warp you'll never get them flat enough to seal. I built a jig for one, 1/2" steel plate that allowed me to bolt down and weld and sit till it cooled. Worked great. It was for my own bike. The only problem is it wasn't any better than the JB fix and I had quite a bit of time invested. The other option is just to buy a new one or find one in a junk yard. Tons of CR 250s out there and chances are you'll have to anyway once you start welding on it.
I don't think I've owned a bike, or my family that dosen't have a little JB some where. There's places for JB and places where welding is a better solution.
Jerod.

[Portable Welder]

Fushion King, Evidently we must be lucky welders.